Secondary Metabolites by Chemical Screening, 24. Oasomycins, New Macrolactones of the Desertomycin Family

Abstract

Abstract New macrolactones, named oasomycin A to D ( 1 to 4 ), were discovered by a chemical screening in the culture broth of Streptoverticillium baldacii subsp. netropse (strain FH‐S 1625). The structures were established by detailed spectroscopic analysis. The fundamental 42‐membered lactone moiety of oasomycin A and B ( 1 and 2 ) is analogous to that of desertomycin A ( 5 ), while the oasomycins C and D ( 3 and 4 ) are the first representatives of macrolactones bearing a 44‐membered skeleton. These metabolites can be distinguished by side chain modifications at C‐41 or C‐43 as well as the presence of an α‐linked D ‐mannose moiety attached to 22‐OH. Due to the structural similarities the oasomycins are integrated into the desertomycin family. In vitro testing by using the HEP‐G2 cell assay showed oasomycin A ( 1 ) to be an inhibitor of de novo cholesterol biosynthesis.